GetRelayStates held d.mux (RLock) while calling into the relay
Manager (RelayStates/RelayConnectError/ServerURLs). Those calls can be
slow or block on the relay manager's own locks while it is reconnecting,
which kept the central Status mutex held and stalled every peer state
writer (UpdatePeerState, ReplaceOfflinePeers, etc.) contending for it.
Guard relayMgr/relayStates with a dedicated muxRelays mutex and release
it before invoking the relay Manager, so the relay read path no longer
contends with the hot peer-state writers on d.mux.
dec95a0757